https://www.yearone.com/Product/1966-74-a-b-e-body/ae340
There you go,and they wont be cracked. who cares if they are not factory stock,whatever used manifolds you will find wont be the factory stock ones for your car anyway.
as an added bonus some of the related items needed for the install are listed aswell:)
if i ever ended up swaping to manifolds thats the way i would go.